Metal thermal spray method

ABSTRACT

Provided is a metal thermal spray method, which does not require a process of imparting an uneven shape to a surface of a base material in advance, 
     A metal thermal spray method of thermally spraying a metal onto a surface ( 1   a ) of a base material ( 1 ) made of a metal, the metal having an ionization tendency larger than that of the metal of the base material ( 1 ), includes: thermally spraying the metal onto the surface ( 1   a ) of the base material ( 1 ); and impregnating a thermally sprayed film ( 2 ) formed by the thermal spraying with a coating material ( 5 ) that contains silane and polyisocyanate and has viscosity of 50 to 500 mPa·s at 25° C. and curing the coating material ( 5 ). In this manner, a pore sealing treatment in the thermally sprayed film ( 2 ) and adhesion strength of the thermally sprayed film ( 2 ) onto the surface ( 1   a ) of the base material are reinforced.

TECHNICAL FIELD

The present invention relates to apply a metal thermal spray to asurface of a base material consisting of a metal such as bridges,towers, pipes, guardrails, ship, and various types of steel.

BACKGROUND ART

In order to impart an anchor effect to a thermally sprayed film, aconventional metal thermal spray method employs a method of obtainingthe anchor effect in such a manner that a base material surface issubjected to blasting in advance to roughen and is formed into an unevenshape or that, as described in Patent Literature 1 below, a basematerial surface is previously coated with a coating film compositioncontaining an epoxy resin to form a coating film having an uneven shapeand a metal thermal spray is applied to the surface having such anuneven shape.

CITATION LIST Patent Literature

Patent Literature 1: JP 3106480 B1

SUMMARY OF INVENTION Technical Problem

In the method of roughening the base material surface by the blastingand forming the uneven shape, however, there are problems that not onlyworking efficiency becomes poor depending on the degree of skill of aworker but also costs become increase.

In addition, according to the method of the Patent Literature 1described above, the blasting becomes unnecessary and thus workingefficiency is improved, but a coating film formed on the entire basematerial surface contains an epoxy resin having high insulation, therebybecoming an insulator, so that the flow of current to the thermallysprayed film from the base material will be blocked.

For this reason, the thermally sprayed film having a larger ionizationtendency than the base material cannot be sacrificially dissolved, andthere is a concern of not being capable of achieving an original purposeof the metal thermal spray, that is, a purpose that the thermallysprayed film is sacrificed instead of the base material and thus thebase material is prevented from becoming rusty.

Solution to Problem

In the present invention, the process of imparting the uneven shape tothe surface of the base material in advance as in the related artdescribed above is eliminated, a metal is directly thermally-sprayedonto the base material surface, and thus an innovative metal thermalspray method is provided in which an adhesion strength between thethermally sprayed film and the surface of the base material isreinforced after the thermally sprayed film formed.

In summary, according to the present invention, a metal thermal spraymethod of thermally spraying a metal onto a surface of a base materialmade of a metal, the metal having an ionization tendency larger thanthat of the metal of the base material, includes: thermally spraying themetal onto the surface of the base material; and impregnating athermally sprayed film formed by the thermal spraying with a coatingmaterial that contains silane and polyisocyanate and has viscosity of 50to 500 mPa·s at 25° C. and curing the coating material, whereby a poresealing treatment in the thermally sprayed film and adhesion strength ofthe thermally sprayed film onto the surface of the base material can bereinforced. Therefore, the base material can be appropriately protected.

Preferably, the coating material contains alkylalkoxysilane as thesilane, and the alkylalkoxysilane and the polyisocyanate contained inthe coating material has a weight ratio of 10 to 90:90 to 10 toeffectively promote a curing reaction of both them.

Advantageous Effects of Invention

According to the metal thermal spray method of the present invention, itis possible to reinforce the adhesion strength of the thermally sprayedfilm in such a manner that the metal can be thermally sprayed onto theflat base material surface without impartment of the uneven shape to thebase material surface and that the thermally sprayed film is impregnatedwith the coating material having low viscosity before curing and highbonding strength after curing, whereby the coating material enters intofins pores present in the thermally sprayed film and is then cured toappropriately seal the fine pores, and the coating material is filledand cured in the fine cavities formed between the back surface of thethermally sprayed film and the surface of the base material.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view schematically illustrating a statewhere a thermally sprayed film is formed on a surface of a base materialwhich is thermally sprayed by a metal.

FIG. 2 is a cross-sectional view schematically illustrating a statewhere the thermally sprayed film is impregnated with a coating materialand the coating material is cured.

DESCRIPTION OF EMBODIMENTS

An embodiment of a metal thermal spray method according to the presentinvention will be described with reference to FIGS. 1 and 2.

As illustrated in FIG. 1, in the metal thermal spray method according tothe present invention, a surface 1 a of abase material 1 is subjected toa scraping treatment using a known disk sander, if necessary, to removecontaminations or oils, a degraded coating film, floating rust, and thelike, and a metal is thermally sprayed onto the surface 1 a of the basematerial 1 using a known thermal spraying machine to form a thermallysprayed film 2.

The thermally sprayed film 2 is formed to have a thickness of 50 to 500μm. The most preferred thickness is 50 to 150 μm.

As the metal to be thermally sprayed, a metal is used that has anionization tendency larger than that of a metal constituting the basematerial 1. For example, when the base material 1 is constituted by iron(steel), zinc, aluminum, or the like is thermally sprayed. Further, athermal spray method is not particularly limited in the presentinvention.

In the state of FIG. 1, a back surface 2 b of the thermally sprayed film2 includes a portion coming in close contact with the surface 1 a of thebase material and a portion apart from the surface 1 a of the basematerial to be formed with fine cavities 4 in a region to line surface 1a of the base material therefrom, and adhesion strength of the thermallysprayed film 2 is in a weak state with respect to the surface 1 a of thebase material toy the presence of the fine cavities 4. In addition, finepores 3 are formed in the thermally sprayed film 2.

In the present invention, from the state of FIG. 1, the front surface 2a of the thermally sprayed film 2 is coated with a coating material 5consisting of a liquid containing silane and polyisocyanate as a mainmaterial, using a known coating means such as a brush, a roller, or aspray, and the thermally sprayed film 2 is impregnated with the coatingmaterial 5.

Preferably, alkylalkoxysilane is used as the silane. Thealkylalkoxysilane reacts with moisture in the air to generate silanoland ethyl alcohol, and the other polyisocyanate reacts with moisture inthe air to generate polyurea and carbon dioxide.

As described above, the silanol to be generated by alteration of thealkylalkoxysilane and the polyurea to be generated by alteration of thepolyisocyanate cause a curing reaction, and exhibit high bondingstrength after the curing. The ethyl alcohol generated from thealkylalkoxysilane is volatized at the time of coating of the coatingmaterial, and the carbon dioxide generated from the polyisocyanate isdispersed at the time of coating of the coating material.

Furthermore, a weight ratio between the alkylalkoxysilane and thepolyisocyanate contained in the coating material 5 is set to be 10 to90:90 to 10 to effectively promote the curing reaction of both them.Mixing examples of the coating material 5 are as follows, and thecoating material 5 does not require a solvent.

MIXING EXAMPLE 1

Amount to be mixed per 1 kg of the coating material 5

Polyisocyanate (liquid) 800 g Alkylalkoxysilane (liquid) 200 g

MIXING EXAMPLE 2

Amount to be mixed per 1 kg of the coating material 5

Polyisocyanate (liquid) 500 g Alkylalkoxysilane (liquid) 500 g

In addition, the coating material 5 is adjusted to be a liquid havinglow viscosity of 50 to 500 mPa·s and preferably 200 mPa·s or less at atemperature of 25° C. by adjustment of the amount of alkylalkoxysilane.

As described above, the coating material 5 having the low viscosityeasily enters into the fine pores 3 formed in the thermally sprayed film2 and easily reaches the fine cavities 4 formed between the back surface2 b of the thermally sprayed film and the surface 1 a of the basematerial through the fine pores 3 at the same time as illustrated inFIG. 2, thereby being filled and cured in the fine cavities 4.

Then, the coating material 5 is cured without a gap in the fine pores 3and is also cured without a gap in the fine cavities 4, and exhibitshigh bonding strength after being cured. The coating material 5 cured inthe fine cavities 4 firmly bonds to the surface 1 a of the base materialand also imparts an anchor effect to the thermally sprayed film 2. Inaddition, a non-impregnated part of the coating material 5 forms astrong coating film 5′ on the front surface 2 a of the thermally sprayedfilm 2.

That is, the coating material 5 enters into the fine pores 3 and is thencured to appropriately seal the fine pores 3, and, at the same time, isfilled and cured in the fine cavities 4 formed between the back surface2 b of the thermally sprayed film and the surface 1 a of the basematerial, whereby the thermally sprayed film 2 and the base material 1can be firmly combined with each other to increase adhesion strength.Furthermore, the costing film 5′ is formed on the front surface 2 a ofthe thermally sprayed film 2 to appropriately protect the thermallysprayed film 2.

In the metal thermal spray method according to the present invention,furthermore, as illustrated in FIGS. 1 and 2, a portion of the backsurface 2 b of the thermally sprayed film 2 comes in close contact withthe surface 1 a of the base material 1, whereby the flow of current tothe thermally sprayed film 2 from the base material 1 is not inhibited;and the thermally sprayed film 2 made of a metal having a largerionization tendency than the metal of the base material 1 issacrificially dissolved, whereby the base material 1 is protected bybeing prevented from becoming rusty as appropriate.

As a result in which the inventors made use of the coating material 5according to each of the mixing examples and carried out a tensile testof the thermally sprayed film using the thermal spray method accordingto the present invention, it was confirmed that the bonding strength of1.5 N/mm² or more was exhibited even when the coating material 5according to any of the mixing examples was used. Specifically, zinc andaluminum were thermally sprayed onto the surface of an iron plate whichwas a base material to form a thermally sprayed film having a thicknessof 200 ηm, the coating material 5 according to each of the mixingexamples was coated on the surface of the thermally sprayed film toimpregnate the thermally sprayed film with the coating material 5, thecoating material 5 was provided with square incisions of which one sidehad a length of 4 cm after being cured, the incision reaching the basematerial, an attachment was attached to the thermally sprayed filmdivided into the square shape, to be pulled using a bonding forcetester, whereby the bonding strength was measured.

As described above, the metal thermal spray method according to thepresent invention does not require a pre-treatment used in theconventional method, the pre-treatment imparting an uneven shape to thesurface of the base material to obtain an anchor effect.

Then, the metal is directly thermally-sprayed onto the surface of thebase material not having the uneven shape, and after the thermallysprayed film is formed, the thermally sprayed film is impregnated withthe coating material, which exhibits the low viscosity before the curingand the high bonding strength after the curing, through the fine pores.In this way, the metal thermal spray method according to the presentinvention is an incommensurable thermal spray method capable of sealingthe fine pores and reinforcing the adhesion strength of the thermallysprayed film.

Furthermore, since the metal thermal spray method according to thepresent invention is a simple method in which the metal is thermallysprayed onto the surface of the base material in a known manner and thethermally sprayed film formed by the thermal spray is coated andimpregnated with the coating material, the metal cap fee effectivelythermally-sprayed onto metal structures such as existing bridges in thefield, especially.

In this description, the numerical range between the lower limit valueand the upper limit value indicated by “to” represents all numericalvalues (integer value and fractional value) between the lower limitvalue and the upper limit value. In appended Claims, the same is alsoapplied.

REFERENCE SIGNS LIST

1 Base material

1 a: Surface of base material

2: Thermally sprayed film

2 a: Front surface of thermally sprayed film

2 b: Back surface of thermally sprayed film

3: Fine pore

4: Fine cavity

5: Coating material

5′: Coating film

1. A metal thermal spray method of thermally spraying a metal onto asurface of a base material made of a metal, the metal having anionization tendency larger than that of the metal of the base material,comprising: thermally spraying the metal onto the surface of the basematerial; and impregnating a thermally sprayed film formed by thethermal spraying with a coating material that contains silane andpolyisocyanate and has viscosity of 50 to 500 mPa·s at 25° C. and curingthe coating material, whereby a pore sealing treatment in the thermallysprayed film and adhesion strength of the thermally sprayed film ontothe surface of the base material are reinforced.
 2. The metal thermalspray method according to claim 1, wherein the coating material containsalkylalkoxysilane as the silane, and the alkylalkoxysilane and thepolyisocyanate contained in the coating material has a weight ratio of10 to 90:90 to 10.